Any filing submitted to the FEC can be amended later by the filer.
Once an amendment is filed, it replaces the original filing and any previous amendments to the original filing completely.
In the section on header rows, we learned that amendments will have a value in the Report Number field of the first line of the electronic filing. The value of the Report Number represents the number of times the original filing has been amended. The easiest way to determine whether any given filing is an amendment is to check whether the Report Number field is blank. If it is, we can move on, confident that this is an original filing. If the field contains a value, we know that the filing is an amendment.
The section on header rows, also taught us that the Report ID field will contain a value on amended filings (and will be blank otherwise, just like the Report Number field):
If the filing is an amendment, the report ID will look like this: FEC-763780
The Report ID tells us which filing this one amends.
For example, filing No. 776795 has this value in the Report ID field: FEC-772249. This means that it amends filing No. 772249. If we have previously saved filing No. 772249 somewhere, we should delete it and instead use the new filing.
Note that amendments themselves do not get amended; only the original filing is amended. If a filing is amended multiple times, when we save the latest amendment, we can discard both the original filing and any previous amendments. Previous amendments can be found by looking at the Report ID field; all amendments to the same original filing will have the same value in that field.